chronograph question

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Interests:Many shooting sports disciplines....from NRA 3 & 4 position smallbore, air rifle, smallbore silhouette, USPSA/IDPA/ICORE NRA Hi Power Rifle,
Also semi-professional trumpet player as well as a real deal bugler and play graveside for deceased veterans and their families.

I don't know of any way to calibrate a personal chrono. Altitude does have a small effect on bullet velocity. Air is denser at sea level and gets less dense the higher in elevation. It is a small difference and I suspect there would little or no noticeable difference for cowboy loads. My big game rifles have ballistic turrets installed on them that are calibrated for my specific loads and I chose 7,000' at the altitude to be set at. It is probably mid elevation for my hunting.

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Elevation should not make a difference AT THE MUZZLE, but will at distance. Temperature however will. The loads that just make power factor on a hot July day after laying in the sun all afternoon might not make it at a winter shoot after a night in the car.

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About the only way to "calibrate" your personal chronograph is to obtain reliable factory ammo that has been tested and the velocities published. Best is to use .22 Long Rifle Match ammo. That won't give you an exact match, but it will be close enough to tell you if something is changing. For example, suppose on the way to the range, your screens get bumped and move on the mounting rail. By firing some of your "standard" rounds, you might see a difference. Keep in mind, however, that the velocity of the "standard" ammo can change with temperature. The timing crystals inside the chronograph unit might change, which could change the readings, but that should only happen if the unit gets old, or suffers an impact.

I think Trailrider is right about using .22 rimfire for checking calibration. I would use target ammo if you have any as they are made to higher standards than normal ammo.

When you check reloading manuals, they usually state the barrel length that was used on the test gun. There is also a standard deviation factor used in calculating the published velocity. When I reload and test the loads, none of them are exactly the same velocity. There are just too many variables involved.

Velocity of even the best .22 Match ammo can Differ a fair amount even in guns with the same barrel lengths ...

CIL m-171 , Marlin and Savage are with 22 inch barrels, all shot with same box of Eley Match ,,, 1,032, 1,003 and 1,009 over my Professional equipment ...

The velocities are the average for 10 shots in each gun ...

The only way to test a unit I know of would be to place it between the screens of professional equipment and shoot through both at the same time a record the readings...

I have checked 3 different "Chrony" units by placing them centered between the screens of my equipment, this is the only way I know of to test eguipment ...

I have found them to give wildly inaccurate readings, one gave a reading 2,700 on a 50gr. bullet fired from my .220 Swift while sitting between my screens my reading for the same 5 shots was 4,080 Fps. with SD of 6 Fps.

I then tested my Sling Shot using a .400 caliber Round Ball the Velocities were Chrony,,, 480 fps. and mine 234 Fps.

I then shot two rounds of 5mm Reminton Mag ( This rimfire ammo ) the velocities were 3,180 and 2,202 Fps.

So unless you can test yours between the sceens of like equipment I know no way to be sure ....

As mentioned previously 22LR ammo is sadly NOT a good choice. A high quality air rifle is better. My radar lab chrono runs a self test every time it is turned on. The inexpensive Chrony units mentioned by J C have had in my testing VERY poor results. The Oehler 35 with the test screen works pretty well but to get accurate results you need either radar or a true lab quality Unit like a Oehler 88 at 10K+.

I have tested two Oehler 35 P units when set-up with a 4 foot spacing of their screens , both units were never more than 1% different than my Pro Equipment that is Not Portable .... So I bought a unit for my self for testing loads under different conditions than what I have at the Shop ...

The testing included Shooting arrows , Air Rifles, Pistols and rifles with Velocities from 980Fps. to 4,453 Fps.

You must be careful to keep the screen spacing right on , but I feel the 35P is a unit that used properly can be trusted ....

I will make a couple of comments First of he used the Oehler with it's closest Screen setting , Placed the Wrong distance from the Muzzle . with the screens tipped and under the worse possible light conditions ... Mottled Shade where the slightest breeze would cause the light to shift and change over different parts of the screens at different times ... I will not say that this was a Known attempt to show the Oehler in the worse possible Light ( ) or if It was a lack of understanding off how Chronographs work...

He does state that he has had a Oehler for years though....

I will state that in my opinion The Oehler is a far more versatile unit and that the MagnetoSpeed is totally useless for use with revolvers ...

It also has a narrow range of use even with rifles , as he states in his piece...

I Will agree that the MagnetoSpeed is Faster and easyer to set-up if you are only doing ONE rifle per session , would I buy ONE ,,, Not a chance...

Are Oehler paying me ,,,,,,, Wish they were ,,,, But Nope !!!

Just this Cowboys opinion after using Chronographs for 33 years to test Firearms of all shapes and sizes ...

I can give you some first hand information on the magnetospeed. It works pretty well but you have to watch it VERY carefully. It must stay exactly in line with the barrel. Just a few degrees off will give false readings. It is also almost impossible to use successfully with a muzzle brake, and as J C mentioned it can't be used with a pistol.

As for light activated chronographs: To work the best the light must be totally controlled. CED and PACT both have IR light sources for theirs that helps with the problem. I have both, and the CED with IR screens is a good as the Oehler 35 in my opinion. IF you move the screens further apart on the Oehler AND control the light it is a bit better. For many years we put chronos in boxes and used incadescent bulbs for light directly over the screens. That worked well with the PACT and CED units. Setting up an inexpensive light chrono outdoors is asking for trouble. It is better than nothing but don't expect results accurate enough to use with a ballistics program.

I have one of the very first LabRadar units. Serial #14. I have been very happy with it. Very accurate and easy to use. You can adjust the sensitivity of the pickup. I haven't noticed any problems using it when other shooters are around. It uses batteries up quickly. Get an external rechargeable USB battery pack.